In recent years, virtual server techniques have been progressing and proliferating. In the virtual server techniques, plural virtual servers are configured on one physical computer using software, and the plural virtual servers perform plural processes in parallel. With the virtual server techniques, it is possible to configure a virtual server system in which plural virtual servers are run at the same time using plural computers connected through a communication network.
Hereinafter, a physical computer is also referred to as a physical server device to distinguish the virtual server from the physical computer.
The virtual server system as described above employs a technique in which virtual servers are integrated using available resources in the physical server device. For example, Patent Document 1 proposes a virtual server system in which a managing virtual server together with other virtual servers are formed on a physical server device having a large amount of available resources, while a physical server designed specifically for management is operated as a management server device in the previous technique. With this method, it is possible to reduce the number of physical server devices. Further, Patent Document 2 proposes a virtual server system in which a virtual machine is transferred between host machines (management units of the virtual machine) on the basis of the amount of resources used for services.